1. Field of the Invention
This invention relates generally to the field of onscreen pointer control for computers, and in particular to devices that incorporate pointer control into a keyboard.
2. Description of the Related Art
Video pointer control devices are commonly used in most personal computer systems and workstations to manipulate an onscreen pointer. Mice are the best known and most common such devices. Most mice fall into two general categories: mechanical and optical. A mechanical mouse employs a roller ball positioned in an aperture in a lower surface of the mouse. The device is configured such that, as the mouse traverses a flat underlying surface, the roller ball rotates inside the mouse. Mechanical and/or optical systems within the mouse detect rotation of the ball in two axes and translate the detected rotation into signals that are transmitted to the computer, which in turn moves a pointer on the screen in accordance with the detected rotation. Such mechanical mouse pointer control devices have been in common use for many years.
Optical mouse pointers are a more recent development. Such a device employs a light emitter and an optical sensor positioned in close proximity to each other on the lower side of the mouse. The emitter, a light emitting diode (LED), for example, illuminates the surface beneath the mouse. As the mouse is moved by a user, the optical sensor detects the movement as variations in the reflected light, in the two axes. This is again transmitted to the computer where an onscreen pointer moves in response.
Another pointer control device includes a gyroscopic sensor configured to detect movement of the device, without reference to an underlying surface, such that it may be operated in free space.
While the mouse is the most common, other types of pointer control devices have come into use for applications where a mouse is impractical. For example, a trackball is a device in which a roller ball is positioned on an upper surface of the device, such that a user manipulates the ball directly to generate a control signal for the screen pointer. Trackballs do not require as much space, since they are stationary. In some cases, the trackball housing is attached to a computer keyboard, or, in the case of some notebook style computers, integrated into a front portion thereof. In other systems, especially of the notebook style, a touch sensitive pad is integrated into the keyboard, or a small knob is positioned between keys of the keyboard. In the latter device, a user presses against the knob to generate the control signals.
Control of an on-screen pointer or cursor may also be carried out via keys of a computer keyboard. For example the arrow keys may be employed in some cases. Additionally, the combined use of the ALT or CTRL keys with other keys, sometimes referred to as chording, may also affect cursor movement, placement, page scrolling, etc.